1. Whisk flour, yeast, and salt together in large bowl. Whisk 6 eggs, water, and sugar together in medium bowl until sugar has dissolved. Whisk in butter until smooth. Add egg mixture to flour mixture and stir with wooden spoon until uniform mass forms and no dry flour remains, about 1 minute. Cover bowl with plastic wrap and let stand for 10 minutes.

2. Holding edge of dough with your fingertips, fold dough over itself by gently lifting and folding edge of dough toward middle. Turn bowl 45 degrees fold again. Turn bowl and fold dough 6 more times (total of 8 folds). Cover with plastic and let rise for 30 minutes. Repeat folding and rising every 30 minutes, 3 more times. After fourth set of folds, cover bowl tightly with plastic and refrigerate for at least 16 hours or up to 48 hours.

3. Transfer dough to well-floured counter and divide into 2 pieces. Remove golf ball-size piece of dough from each. Pat 2 large pieces of dough into 4-inch disks and 2 small pieces of dough into 1/2-inch disks. Working with 1 piece of dough at a time, work around circumference of dough; fold edges of dough toward center until ball forms. Flip dough over and, without applying pressure, move your hands in small circular motions to form dough into smooth, taut round. (Tackiness of dough against counter and circular motion should work dough into smooth, even ball, but if dough sticks to your hands, lightly dust top of dough with flour.) Repeat with remaining dough. Cover dough rounds loosely with plastic and let rest for 5 minutes.

4. Grease two 8 to 8 1/2-inch fluted brioche pans. After 5 minutes, flip each dough ball so seam side is facing up, pat into 4-inch and 1/2-inch disks, and repeat rounding step. Place larger rounds, seam side down, into prepared pans and press gently into corners. Place smaller rounds, seam side down, in center of larger rounds, pushing down gently so only top halves of smaller rounds are showing. Cover loaves loosely with plastic and let rise at room temperature until almost doubled in size (dough should rise to about 1/2 inch below top edge of pan), 1 1/2 to 2 hours. Thirty minutes before baking, adjust oven rack to middle position, place baking stone on rack, and heat oven to 350°F.

5. Remove plastic and brush loaves gently with remaining 1 egg beaten with salt. Set pans on stone and bake until golden brown and internal temperature registers 190°F, 35 to 45 minutes, rotating pans halfway through baking. Transfer pans to wire rack and let cool for 5 minutes. Remove loaves from pans, return to wire rack, and let cool completely before slicing and serving, about 2 hours.

Makes 2 loaves